Luminescent tube and system



March 2 1943. c. P. BOUCHER LUMIiIESCENT TUBE AND SYSTEM Original Filed May 22. 1337 2 Sheets-Sheet 1 March 2 1943. c. P. BOUCHER LUMINESCENT TUBE AND SYSTEM 2 Shets-Sheet 2 Original Filed May 22, 1937 CkaJ-ZeaPBaucker flTrO/PNfiY Patented Mar. 2, 1943 LUIVIINESCENT TUBE AND SYSTEM Charles Philippe Boucher, Paterson, N. J., assignor to Boucher Inventions, Ltd., Washington, D. 0., a corporation of Delaware Original application May 22, 1937, Serial No. 144,285. Divided and this application August 21, 1939, Serial No. 291,204

4 Claims.

This application is a division of my cop-ending application, Serial Number 144,285, filed May 22, 1937, and entitled Luminescent tube and system, now U. S. Letters Patent 2,190,009,

issued February 13, 1940, and the invention re-' the component beams merge and blend with each other to produce the final, composite beam. 7

Another object is the production of a luminescent tube system of the character described which is peculiarly adapted to give bril-- liant, eificient and uniform operation over long periods of use with a minimum of attention and/or repairr Still another object is the production of high voltage luminescent tube systems and apparatus for the production of a composite beam of' light of selected quality and color, in which condensive effects and other electrical break-down phenomena are reduced to a minimum and which are well adapted to withstand the many varying conditions encountered in actual practical use. Other objects will be apparent in part, and in part pointed out hereinafter.

The invention accordingly consists in the com bination of elements, features of construction and arrangement of parts as described herein, the scope of the application of which is indicated in the following claims.

In the accompanying drawings:

Figure 1 represents a luminescent tube system and apparatus in accordance with my invention, certain parts being broken away to more clearly disclose other parts and certain parts being illustrated diagrammatically,

"Figure 2 is a cross-sectional View, on an enlarged scale, of certain portions of the apparatus as seen at the line 2-2 of Figure 1 looking in thedirection of the arrows,

Figures 3 and 4 respectively represent longi-' tudinal and cross-sections of a modified luminescent tube construction, and

' Figure 5 represents a luminescent tube system which is a modification of the system shown in Figure 1.

Like reference characters denote like parts throughout the several views of the drawings.

As conducive to a clearer understanding of certain features of my invention, it is to be noted at this point that although luminescent tube systems and apparatus have come into widespread use in the display and industrial arts, as witness the familiar orange-red neon signs or displays of stores and theatres, and the blue mercury-arc lamps used in printing industries and the like, the art has so far been limited, from a practical standpoint, to a few basic or fundamental colors. These are the characteristic radiations of the elemental gases when energized. In display work a variety of colors is often desirable from a standpoint of novelty and appeal to the eye. In the industrial arts, however, little has been accomplished in obtaining a true white light, with its absence of detrimental shadow, and its case on the eyes. In this the art has progressed but little since its pioneer days, despite the considerable research activity along those lines. I

While it has been recognized that, along the lines of conventional teachings of physics, it is theoretically possible and perfectly feasible to compound the radiation from a plurality of luminescent tube sources to produce the desired composite light, as a practical matter but little of a commercially feasible nature has been proposed. In short, the art of compounding radiation from a plurality of luminescent tubes, each of a diiferent color characteristic, has been at a practical standstill.

In all such composition of radiation, as for example, in the production of light approximating the quality of sunlight, it is necessary to place the tubes, each capable of producing a light of characteristic color, in a side by side relationship and as close together as possible, in order to facilitate the light blending, as well as to minimize the over all dimensions of the assemblage, for economic and aesthetic purposes. When comparatively low operating voltages are used, the spacing between the tubes can be quite small, even almost infinitesimal, so that the quality of the light resulting, considered apart from the aspects of production, is reasonably satisfactory. It is apparent, however, that when low voltages are employed, the lengths of the tubes become quite limited. Instead of being able to use the comparatively economical long tube, a plurality of short tubes must be used. This increases the cost of installation. In addition, the use of short lengths of gaseous discharge tubing always is not possible because of structural limitations in the luminescent display.

An object of my invention, therefore, is to eliminate the foregoing disadvantages, and in so doing, to cheapen the installation and operating costs, as well as to carry out the proper blending of light with comparatively long tubes of high voltage characteristics. 5

The art also has investigated the use of high voltage tubes for the emission of the components of blended radiation. As intimated in the fore-' J going, high voltage tubes are moresatisfactory to work with because they are easier to make up into display signs, and more economical to operate per unit of emission. Here, however, the ef forts of the investigators have met with but little g practical success. Ordinary elongated tubes of the art were employed. Because of the high voltages at which the tubes were operated, the investigators found that if the tubes were placed close together side by side, as is essential for completely satisfactory blending, then because of the difference of potential existing between adjacent portions of the tube, condensive action occurred, the resulting strains frequently resulting in a rupture of the walls of the tubes. I

To prevent this disruptive and disastrous condensive action, the tubes were separated a safe distance. Unfortunately, under these conditions: of operation, poor blending of the light rays resulted, as well as unsatisfactory distribution of illumination. Considerable fringing around theshadows occurs, i. e. the fundamental blue, red, yellow colors of the spectrum, as Well as green, are found around the shadows produced by modern tube lighting. These drawbacks make such sources of blended lightunsuitable for many important purposes, such as motion picture studios, p ojec n beams a d h l e in n us a and; home illumination. Furthermore, this necessityof spacing apart the component tubes materiallyincreases the costsof a given installation.

An object of my invention, therefore, is substantially to eliminate the difiiculties encountered hitherto in the use of high voltage gaseous discharge tubes in the production of composite radiatiQ i and also to operate comparatively great lengths of luminescentgaseous discharge; tubin for such purpose without the harmful condensive effects heretofore encountered,

Referring now more particularly to the practice; of my invention, attention is directed to-Figure 1. of the drawings wherein luminescent tube apparatus generally indicated at it] is energized byhigh potential electrical transformer apparatus H supplied with alternating current electrical energy at, say, 60 cycles, 110 volts, by source of supply l2.

Luminescent tube apparatus Iii (see also Figure 2) consists of an elongated gaseous discharge tube. I3 having a collapsed wall portion [3a into. which is fitted a second elongated gaseous discharge tube M.

The tube 13 illustratively containsa gas. such: as neon at a very low pressure. In order that its, walls may Withstand the atmospheric pressure exerted on them and, further, in order that a fairly uniform luminescence be preserved throughout a broad field of vision, the tube is substantially crescent-shaped in cross-section (see Figure 2); The curvature of the inner or concave portion 3a conforms to that of; the sec n n s en u e. n Qr ri a oo QQnr] tact with a minimum spacing be preserved between the tubes. The curvature of the outer wall l3b of tube i3 is regular and assures a gradual and uniform change in the gas space of the tube in progressing from a center part of the tube in either direction. At the edges I30 and 13a. of the tube, the curvature is such as to give a sufiiciently narrow gas-space and yet permit adequate strength of these points.

Tubes I3 and M are maintained in proper contact relationship by means of suitable spring clips l5. Preferably these clips are fashioned of non-magnetic stainless steel. The clips hold the tubes 13 and M in loosely interiitting relation, so that the tubes are free to slide longitudinally relative to each other. Stainless steel clips have I the further advantage of serving as a reflector which is always .clear and has high reflecting properties for light emitted by the tubes. Because'of the non-magnetic character of the clips [5 no magnetic pull is exerted on the conductive column of gas in the tubes and operation of the tubes is, therefore, unaffected thereby.

Good results are obtained when the metal is applied in sections along the lengths of the tubes, as in Figure 1, spaced apart a convenient dis-v tance, say roughly sh" to Such spacing is sufficient to avoid any harmful condenser action between any two widely spaced points along the.- length of the same tube. These reflector clips, may be made as long as six inches without detrimental condensive action.

Absolute freedom of the tubes to slide relatively to each other is essential, especially when the two tubes are fashioned of different glasses. To the end of securing the tubes together by means of the reflecting clips 15 in orderto assure complete freedom of longitudinal motion, I conveniently strike up bosses or ridges Hie along the outer sides of tube (see Figure 2). These appear near the region where the reentrant wall I39 starts. The ends 15a of clips ['5 are shown as inwardly curved so as to snap downwardly and over the said bosses; By tension, clips 15 are firmly secured against the tube [3. The compressive action of the middle part 15b of clip l5, as seen in Figure 2-, insures that tube M is forced'firmly against the tube, l3.

A further function of clips liis. to provide a reflector for the light emitted by luminescent tubes.

Band [4. Where desired, however, tubes [3 and. [4 may be secured together in any,v suitable mannerandrefiector means provided. such asmetal foil secured to the tube by insulating varnish. Likewise, some molded composition having an inner surface coated; with a desired reflecting substance is. satisfactory. In this construction both the molded composition; as well as the surfacev coating are electrical insulators in order to. assure a freedom from disturbing the potential gradients along the tubes as a result of the. applied operating potentials.

Luminescent tube i l illustratively contains a. mixture of gases, such as neon and mercury vapor, at a, desired pressure. Preferably the sectionalarea of tube I4 is such as to give a high current density and emit intense visible radiation. Gonveniently, this tube is designated as the light emitting tube. Th tube 113,: in, comparison, is preferably of such sectional area as to employ a. comparatively low current density. The light emitted from this. tube is, justlsufficientin;.co1orand intensity as to supply any, deficiency coming:

this tube I4 is designated as the blending tube. Both'tubes, however, are preferably of lik fourrent-energizing capacity as well as striking potential, for reasons as appear more fully'hereinafter.

Because of the relatively high current densities to be used in the operation of gaseous discharge tube 14, this tube is of smaller area than tube l3. The blending tube l3 may be of comparatively slight luminosity as desired.

In the production of white light, for example, the tube l4 may consist of magnesia glass colored very slightly yellow and known to the trade as canary tubing. It is filled with neon gas to which is added mercury. Upon energization of this gaseous discharge device a light green light is emitted. This light, of course, is in the form of a soft glow characteristic of gaseous discharge tubes, the green color resulting from a filtration of the violet light of mercury vapor through the yellow glass walls of th canary tubing. The crescent-sectioned blending tube 13 may be as nearly colorless and transparent as possible. For this purpose the tube It may be made of soda glass tubing containing neon at low pressure. Energization of this tube, in a manner more particularly described hereinafter, produces a dull orange glow so characteristic of neon.

Because of the relative positioning of the lightemitting tube 14 and the blending tube iii, the orange-red characteristic radiation of tub I73 combines with and supplements the greater volume of pale green light coming from tube [4. This efiect is greatly aided by the reflector clips l5 spaced along the lengths of tubes i3 and I4 and securing these tubes together. By this blending and filtration there is produced the desired composite white radiation. It will be understood that where desired either one of the gaseous discharge tubes may consist of a mixture of inert gases giving off desired light in matters of color and intensity to achieve the required composite result.

Since blending tube i3 is preferably operated at comparatively low current densities, it can be formed of soda glass. This glass tubing is satisfactory for densities of, say -60 milli-amperes without undue overheating. On the other hand, since tube H5 is preferably operated at high current densities, hard glass such as Pyrex or Onyx or like magnesia glass is employed. The magnesia glass tubing is advantageously employed, despite its comparatively high cost, for current densities in excess of 60 milli-amperes.

In order that efiicient illumination may be achieved at a minimum expense of installation, operation and maintenance, tubes l3 and H! are comparatively long. Of necessity they are operated at high voltages, that is, on the order of some 5,000 to 15,000 volts or more. As pointed out hereinbefore, dimculty has previously been encountered in successfully operating parallel gaseous discharge tubes at such voltages. For satisfactory results, these tubes I3 and M are disposed in mechanically parallel relationship, that is, side by side, and closely adjacent each other. Where they are spaced apart any appreciable distance, fringing or breaking up of the light into the primary and secondary spectral colors takes place at the shadows. Furthermore, poor blending of the component light beams and directional transmission of the composite beam also results. Certain objections are encountered inthis construction as indicated above in discussing certain practices of the prior art. vThus, when the gaseous discharge tubes are placed adiacentto each other,

and high voltages are then impressed across the terminals of the tubes, the gas columns present in the tubes are good conductors. The glass Walls of the tubes serve as the dielectrics. A condenser is formed thereby which may be of such capacity, which with the inductance of the transformer secondary winding, gives rise to electrical oscillation producing exceedingly high peak voltages. These voltages may puncture the insulation of the coils of the secondary windings. Furthermore, the high voltage strains produced at contiguous points along the lengths of the tubes may be sufficient to rupture the tube walls.

In accordance with the provisions of my invention, I avoid the aforementioned difficulties in an ingenious manner. Thus, considering Figure 1 of the drawings, it is to be noted that the tubes I3 and M are of'substantially the same length. It will be observed that the discharge space is substantially the same for both tubes. The relative gas pressures are such that the resistivity 'per unit of length of the tubes also is approximately equal. To this end, and since the tube I3 is of a crescent-cross-section throughout the great part of its length must be of substan-' tially full circular cross-section in the region of the electrodes, I find it desirable to bend the ends Ida and [4b of tube 14 upwardly, out of the plane of the tube l 3. In this manner the interelectrode space in tubes 13 and I4 is substantially the same.

. This equality of 1ength for the two tubes alone is not sufi'icient. While the potential drop along the length of each tube is equal in both cases, giving equal potential gradients along the lengthsof the tubes, nevertheless if the current flow in the two tubes is in opposite directionsthe voltage diiference between any two points contiguous to each other along the lengths of the tubes will be approximately the full voltage impressed across the terminals of the tube. Such a potential diiference would result in a rupture of the tube walls. The controlling requirement is that the voltage and directional gradients in the two tubes be substantially equal. One element of this definition is satisfied by making the tubes of equal length. The other is satisfied by. impressing voltages of equal values and of like phase across corresponding terminals of the tubes. 7

Accordingly, in the practice of my invention; I employ a transformer having a single primary winding and two secondary windings; As schematically illustrated in Figure 1 of the drawings, this transformer generally indicated at H has a primary winding l6 supplied from a suitable single-phase source of alternating current electrical'energy 12 by way of conductors I! and I8. Transformer H also includes two secondary winding l9 and 20, each comprising two coil sec tlons, ISa and I91) for winding i 9 and 20a and 20b for winding 29. The coil sections of each winding are wound in the same direction and are connected together in series aiding relationship; The midpoints of the two secondary windings I9 and 20 are grounded as at 2| and 22 respectively. In this way the voltage of the terminals of the secondary windings with respect to ground amounts to only half the potential difference between pairs of terminals. Primary winding I 6 ,,is electromagnetically linked with secondary windings l9 and 20 by way of aniron core generally indicated at 23. Preferably the core construction is such. as to permit a high leakage reactance of the transformer under load condi-' tions.

Now in order that the individual luminescent tubes l3 and I4 comprising the luminescent display Ill be subject to like potential gradients at contiguous points along their lengths, corresponding terminals of the tubes are connected to corresponding terminals of the two secondary windings. Thus, corresponding terminals l3h and Nb of tubes 13 and 14 are connected by way of conductors 24 and 25 to corresponding terminals 2&{0 and [9c of transformer secondary windings 2i! and I9 respectively. Likewise, corresponding tube terminals I37" and M1 are connected by conductors 26 and 21 to corresponding secondary winding terminals 2M and led. By this construction, for an assumed point in the cycle of operation where the current, acting under an induced electromotive force in secondary winding 20 in a downwardly direction as seen in the drawing, flows from winding 20 by way of terminal 290, conductor 24, gaseous discharge tube It, conductor 26 back to winding 20 to complete the circuit. A similar flow of current takes place in tube Hi. In connection with the energization of this luminescent tube the current, acting under a. corresponding electromotive force induced in winding l9, flows from winding I!) by way of terminal I90, conductor 25, tube I4, conductor 21, returning through winding terminal 19d to complete the circuit. For the assumed period in the cycle of operation the flow of current in tubes 13 and I4 is from left to right as seen in the drawings.

Because of the substantial identity of the elec-tromotive forces induced in secondary wind,- ings 2e and i9 and the equivalency of the lengths of tubes l3 and M, as well as their striking voltages and operating currents, the potential; drops along both tubes are substantially the same. This identity in potential'drop with length, orvoltage gradient, assures a freedom from voltage d-iiferences suficient to rupture the walls of the gaseous discharge tubes. In addition, this equivalency of potential gradient at various contiguous points along the lengths of the tubes precludes condensive effects between tubes, thereby preventing the establishment of oscillating conditions and the arising of electrical potentialsdestructive to the transformer secondary wind ings.

In the operation of my luminescent tube system and apparatus a balanced condition of operation is assured at all times by virtue of like transformer secondary windings and the ground-- ing of each of these windings at its midpoint... While corresponding terminals [3h and [4h of tubes l3 and Ht are at, for example, maximum nescent display comprising parallel gaseous discharge tubes-one mounted within another.

positive potential with respect to. ground, the

corresponding terminals I3 and IM will be at maximum negative potential. Similarly, when: tube terminals I3 and My are at maximum positive potential with respect to ground tube terminals Hit and Mn will be at maximum negative potential. Symmetry, therefore, is. always pre served in the operation of the system. v

By my novel luminescent tube system and apparatus, light emission of from 45 to 40. lumens per watt input of electrical energy is obtained as contrasted with the ordinary incandescent lamp of 12 to 15 lumens per watt input.

' While in the illustrative embodiment of my invention discussed above parallel nested luminescent tubes are employed, certain advantages. and economies are realized by employing a lumi- Thus, referring to Figures 3 and 4 of the drawings the tube 30, similar in purpose to tube l3 of Figures 1 and 2, is substantially circular in section. Since this tube ordinarily serves as the blending tube, and hence usually operates at comparatively 10W current densities, tube 30 conveniently is fashioned of soda glass just as in the case of tube l3. Thetube 3|, which is similar to the tube M of the embodiment indicated in Figures 1 and 2, is disposed entirely within the tube 36.

The two tubes 3%) and 3t are sealed together in any suitable manner. Conveniently, the inner tube 3| is maintained. in desired position in tube 30 by means of the incoming terminal member 32. This terminal member is preferably fashioned of a heat-resisting conducting material, such as non-magnetic stainless steel, which possesses sufficient strength at thehigh temperatures reached in the tube to maintain the inner tube in proper position and yet which yields sufiiciently to accommodate the difference in expansion between tubes 35 and 3|. Since tube 3! is run at comparatively high current densities, this tube is preferably formed of heatresistant glass, such as Pyrex or the like.

In order to enjoy maximum benefit in the operation of the luminescent display disclosed in Figures 3 and 4, reflectors 3.3 are spaced along the length of tube 30. Tube 3| is disposed eccentrically Within the tube 30, so that it lies closely adjacent the reflectors 33. The desirability of this eccentricity is dictated by the fact that illuminated displays usually face in one direction only. The radiation, therefore, is thrown in that direction. The eccentricity of the positioning of tube 3| Within tube 39 is further necessitated by a desire to achieve a proper blending and diffused reflection of the light emitted by the two tubes. When tube 3! is disposed centrally of tube 35!, unsatisfactory reflection results, and improper blending occurs,..re-

' sulting in detrimental and undesirable fringing in the shadows.

The construction of my luminescent tube display in accordance with the embodiment. shown in Figures 3 and 4 possesses the material advantage that the direct radiation from the principal source passes through only two glass walls (its own and one wall of tube 30) on its journey to the exterior. In the case of the embodiment illustrated in Figures 1 and 2, the radiation must pass through one wall of tube i4 and both walls of tube l3, resulting in somewhat higher refraction of rays and more absorption. Asa result the arrangement indicated in Figures 3 and 4 is more. efficient than that of Figures 1 and 2. There is the further advantage, in connection with the embodiment of Figures 3 and 4, in that the assembly is neater and more compact. The spring action of clip reflectors 33, where these reflector elements are formed of spring clips, serves no other purpose than to secure the clips to the tube 30. The clips no longer are relied upon to hold the two tubes together.

While in the embodiment of my invention,'as illustratively described above in connection with Figures 1 and 2, more specifically relates to the operation of a luminescent display comprising two tubes by means of electrical transformer apparatus having two secondary windings, certain advantages are realized where two luminescent displays are operated from a-single transformer of the double type, that is, having two secondary windings. Thus, turning to Figure of the drawings, the two luminescent displays and 4| are supplied with alternating current electrical energy at a desired high potential by double transformer 42a.

Displays 40 and 4! are shown as comprising small tubes 42 and 43, respectively, nested in the crescent-shaped recesses of the corresponding larger tubes 44 and 45. All tubes are of substantially the same length in order to achieve a uniform distribution of potential throughout the lengths of the tubes. The two tubes comprising each display are secured together in any suitable manner. Sufficient freedom of motion is permitted, however, to accommodate the difference in longitudinal expansion of associated tubes.

The two luminescent displays 40 and 4| are supplied with high potential alternating current electrical energy from the two secondary windings 46 and 41 of transformer 42a diagrammatically illustrated as interlinking primary winding 48 through an iron core generally designated as 49. Alternating current electrical energy, for example, single phase 60 cycle, 110 volts, coming from the source of supply 53, serves to excite primary winding 46.

In the double transformer illustrated in Fig ure 5 each secondary winding 46 and 41 respectively consists of two coil sections 46a and 46b and 41a and 41b connected in opposed phase relationship, that is, with the induced electromotive forces bucking each other and preventing a flow of current from one coil section into the related coil section. This is generally indicated in Figure 5, for one point in the cycle of operation of the transformer by the arrows located above the coi1 sections of the secondary windings.

Energization of tubes 43 and 45 comprising display 4| is effected from the respective coil sections 4% and 41b of secondary windings 45 and 41. Alternating current electrical energy for coil section 462) is supplied tube 43 by way of conductor 5| and returns through conductors 52, 53 and ground 54. It is to be particularly noted that potentials corresponding in direction and intensity are impressed across the terminals of tubes of display 4|. Therefore, the potential gradients at corresponding points along the tubes 43 and 45 are identical and freedom from condensive effects and high voltage rupture of the tube walls is thus assured.

Similarly, tubes 42 and 44 of display 40 are respectively energized by coil sections 4101. and 48a by way of conductor 51, tube 42, conductors 58 and 53, and ground 43 (for the tube 42) and by way of conductor 59, tube 44, conductors 60 and 53, and ground 54 for tube 44. Here again like potentials are applied to corresponding terminals of the associated tubes of the luminescent display. Condensive effects and otherwise disturbing efiects are thus prevented.

Because of the symmetrical relationship between the two luminescent display apparatus and the energizing transformer apparatus of like symmetry, balanced operation with corresponding high eificiency and freedom from disturbing high potential transient efiects is achieved. In

this embodiment of my invention, however, it

reference to Figure 1, the luminescent tubes are only'of one-half the length and voltage rating although the same current rating may be preserved. '1

Thus it will be, seen that there has been provided in this invention a luminescent tube system and apparatus in which the various objects hereinbefore noted, together with many practical advantages, are successfully achieved. It will be seen that the apparatus is simple, compact, efiicient and thoroughly reliable, and furthermore, that it is well adapted to give desired intense illumination of a desired color or combination of colors. While as illustrative of the practice of my invention the blending of illumination from two gaseous discharge tubes is discussed, it will be understood that, where desired, light from three, four or even more luminescent tubes may be composed, it being necessary, however, that the luminescent tubes be maintained in intimate parallel association and that they be energized from sources of like potential maintained in synchronism as by using a three, four or more secondary winding transformer of proper symmetry.

Since many possible embodiments may be made of my invention and since many changes may be made in the embodiments hereinbefore set forth, it will be understood that all matter described herein, or shown in the drawings, is to be interpreted as illustrative, and not in a limiting sense.

I claim:

1. Ltu'ninescent tube apparatus comprising in combination, a luminescent tube, a second tube maintained in contiguous associated relationship therewith, and transformer means having a common core and including two individual and electrically independent secondary windings having their mid-points grounded and connected in like phase relationship with said luminescent tubes by corresponding ends of said secondary windings being connected to corresponding ends of said tubes.

2. Luminescent tube apparatus comprising in combination, a pair of luminescent tubes maintained in associated contiguous relationship, and a high leakage reactance transformer including two individual and electrically independent secondary windings connected to said tubes in like phase relationship with respect to said tubes by corresponding ends of said secondary windings being connected to corresponding ends of said tubes.

3. Luminescent tube apparatus comprising in combination, a plurality of luminescent tubes maintained in parallel and contiguous relationship, an electrical transformer including a primary winding and a plurality of individual and electrically independent secondary windings corresponding in number to said tubes, alternating current means supplying electrical energy to the primary winding of said transformer, and means connecting corresponding terminals of said sec ondary windings to corresponding terminals of said luminescent tubes, whereby synchronous operation of the tubes is assured and the potential difference existing between contiguous portions of the tubes throughout their lengths is substantially negligible and disruptive discharge between the tubes is effectively precluded.

4. Luminescent tube apparatus comprising in combination, two groups of luminescent tubes, each group consisting of two tubes maintained in contiguous parallel relationship, a high leakage ,reactance transformer including two sec:- of tubes is assured and the potential difference ondary windings, each with its mid-point existing between the contiguous portions of the grounded, means interconnecting adjacent ends tubes throughout their lengths is substantially of the tubes comprising each group to like ends negligible and disruptive discharge between the of the secondary windings, and means connect- 5 tubes of each group is effectively precluded. ing with the other ends of said tubes to ground,

whereby synchronous operation of both groups CHARLES PHILIPPE BOUCHER. 

